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<head><meta charset="utf-8"><title>weekly meeting November 6 · t-compiler/wg-nll · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/index.html">t-compiler/wg-nll</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html">weekly meeting November 6</a></h3>

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<a name="146892105"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892105" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892105">(Nov 06 2018 at 20:32)</a>:</h4>
<p>hi <span class="user-group-mention" data-user-group-id="491">@WG-compiler-nll</span></p>



<a name="146892116"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892116" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892116">(Nov 06 2018 at 20:32)</a>:</h4>
<p>sorry I'm a little late (and I failed to send a note earlier like I normally do)</p>



<a name="146892163"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892163" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892163">(Nov 06 2018 at 20:33)</a>:</h4>
<p>so I don't know if we'll see <span class="user-mention" data-user-id="116009">@nikomatsakis</span> today, since they are busy at SPLASH</p>



<a name="146892230"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892230" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892230">(Nov 06 2018 at 20:34)</a>:</h4>
<p>but I'm hoping there isn't too much that would need their attention anyway...</p>



<a name="146892259"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892259" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892259">(Nov 06 2018 at 20:34)</a>:</h4>
<p>I went through the list of <a href="https://paper.dropbox.com/doc/Non-lexical-lifetimes-NLL-Triage--ARI~s_vcluCqIAV279~5_vX8Ag-Em2cJrvxQMMFWLE7lE5Be" target="_blank" title="https://paper.dropbox.com/doc/Non-lexical-lifetimes-NLL-Triage--ARI~s_vcluCqIAV279~5_vX8Ag-Em2cJrvxQMMFWLE7lE5Be">NLL triage</a> topics earlier today, as you can see if you go look at the <a href="#narrow/stream/122657-wg-nll/subject/making.20plans" title="#narrow/stream/122657-wg-nll/subject/making.20plans">"making plans"</a> topic from earlier today</p>



<a name="146892299"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892299" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892299">(Nov 06 2018 at 20:35)</a>:</h4>
<p>the main two things from that exercise are the following</p>



<a name="146892364"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892364" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892364">(Nov 06 2018 at 20:36)</a>:</h4>
<p>1. who can/should we assign to resolve each of the <a href="https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AA-NLL+-label%3ANLL-deferred+-label%3ANLL-fixed-by-NLL+no%3Aassignee+milestone%3A%22Rust+2018+Release%22" target="_blank" title="https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AA-NLL+-label%3ANLL-deferred+-label%3ANLL-fixed-by-NLL+no%3Aassignee+milestone%3A%22Rust+2018+Release%22">two issues</a> that are currently on the Release milestone?</p>



<a name="146892392"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892392" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892392">(Nov 06 2018 at 20:36)</a>:</h4>
<p>2. what P-level should we assign to "[regression - rust2018]: unused_mut lint false positives on nightly" <a href="https://github.com/rust-lang/rust/issues/55344" target="_blank" title="https://github.com/rust-lang/rust/issues/55344">#55344</a></p>



<a name="146892398"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892398" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892398">(Nov 06 2018 at 20:36)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/issues/54943" target="_blank" title="https://github.com/rust-lang/rust/issues/54943">#54943</a> doesn't apply to migrate mode</p>



<a name="146892423"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892423" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892423">(Nov 06 2018 at 20:37)</a>:</h4>
<p>it doesn't?</p>



<a name="146892451"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892451" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892451">(Nov 06 2018 at 20:37)</a>:</h4>
<p>things that compile in migrate mode and shouldn't seem like they apply to migrate mode, no?</p>



<a name="146892514"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892514" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892514">(Nov 06 2018 at 20:38)</a>:</h4>
<p>It doesn't compile in migrate mode, the same as with AST</p>



<a name="146892524"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892524" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892524">(Nov 06 2018 at 20:38)</a>:</h4>
<p>(that is, my rule of thumb is that only issues that are NLL-complete get to go through the migration loophole) ... Or are you saying that since the migration mode does the old region checking, <a href="https://github.com/rust-lang/rust/issues/54943" target="_blank" title="https://github.com/rust-lang/rust/issues/54943">#54943</a> doesn't apply to it?</p>



<a name="146892525"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892525" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892525">(Nov 06 2018 at 20:38)</a>:</h4>
<p>oh that's fantastic</p>



<a name="146892527"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892527" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892527">(Nov 06 2018 at 20:38)</a>:</h4>
<p>woot</p>



<a name="146892574"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892574" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892574">(Nov 06 2018 at 20:39)</a>:</h4>
<p>should it remain P-high ?</p>



<a name="146892590"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892590" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> davidtwco <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892590">(Nov 06 2018 at 20:39)</a>:</h4>
<p>I glanced at the issues and didn't feel confident that I'd be able to make much headway on either.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892657" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892657">(Nov 06 2018 at 20:40)</a>:</h4>
<p>oh man I even wrote a comment explaining all of this 3 weeks ago</p>



<a name="146892672"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892672" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892672">(Nov 06 2018 at 20:40)</a>:</h4>
<p>It's probably higher priority that anything else NLL related that I currently have any plans to work on, if that's anything to go by.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892703" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892703">(Nov 06 2018 at 20:41)</a>:</h4>
<p>okay I'm going to leave it as P-high</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892825" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892825">(Nov 06 2018 at 20:42)</a>:</h4>
<p>and I'll assign it to myself for now, to try to keep it properly on my radar</p>



<a name="146892965"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892965" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892965">(Nov 06 2018 at 20:44)</a>:</h4>
<p>I have to be up front though: I am going to go on leave once my twins are born, which will happen sometime in the next 5 to 10 days...</p>



<a name="146892978"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892978" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892978">(Nov 06 2018 at 20:45)</a>:</h4>
<p>so anything that I take could quite likely get quickly unassigned from me</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146892997" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146892997">(Nov 06 2018 at 20:45)</a>:</h4>
<p>anyway,  I'll leave <a href="https://github.com/rust-lang/rust/issues/55511" target="_blank" title="https://github.com/rust-lang/rust/issues/55511">#55511</a> unassigned for now. Maybe I'll find time to look at it</p>



<a name="146893008"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893008" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893008">(Nov 06 2018 at 20:45)</a>:</h4>
<p>The <em>other</em> topic then was what to do with "[regression - rust2018]: unused_mut lint false positives on nightly" <a href="https://github.com/rust-lang/rust/issues/55344" target="_blank" title="https://github.com/rust-lang/rust/issues/55344">#55344</a></p>



<a name="146893091"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893091" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893091">(Nov 06 2018 at 20:46)</a>:</h4>
<p>personally I don't think it would be a disaster  if this takes a while to get addressed...</p>



<a name="146893101"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893101" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> davidtwco <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893101">(Nov 06 2018 at 20:46)</a>:</h4>
<p>I could look into that.</p>



<a name="146893112"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893112" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> davidtwco <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893112">(Nov 06 2018 at 20:47)</a>:</h4>
<p>I notice you're assigned, so only if you aren't already.</p>



<a name="146893141"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893141" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893141">(Nov 06 2018 at 20:47)</a>:</h4>
<p>I think it would be good for you to take it</p>



<a name="146893199"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893199" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893199">(Nov 06 2018 at 20:48)</a>:</h4>
<p>The only thing that we would fix is the lint?</p>



<a name="146893208"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893208" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893208">(Nov 06 2018 at 20:48)</a>:</h4>
<p>I don't know</p>



<a name="146893213"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893213" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893213">(Nov 06 2018 at 20:48)</a>:</h4>
<p>It depends on what strategy we take</p>



<a name="146893222"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893222" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893222">(Nov 06 2018 at 20:48)</a>:</h4>
<p>Which requires some exploration of the options</p>



<a name="146893244"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893244" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893244">(Nov 06 2018 at 20:49)</a>:</h4>
<p>one of the options I was considering was to have the various lints for the uses (or lack thereof) of a local variable not fire if the local variable's <em>declaration</em> is itself not reachable</p>



<a name="146893326"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893326" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893326">(Nov 06 2018 at 20:50)</a>:</h4>
<p>(And maybe introduce a single new warning saying that the declaration is dead code.)</p>



<a name="146893346"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893346" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893346">(Nov 06 2018 at 20:50)</a>:</h4>
<p>(at least, from what I can tell we <em>don't</em> do that today, and we could...)</p>



<a name="146893355"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893355" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893355">(Nov 06 2018 at 20:50)</a>:</h4>
<p>But its also possible that any decision here would turn into a big bikeshed discussion. (with lots of stakeholders outside of NLL) :(</p>



<a name="146893366"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893366" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893366">(Nov 06 2018 at 20:51)</a>:</h4>
<p>If we want to do more than that we should definitely have some idea before December</p>



<a name="146893377"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893377" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893377">(Nov 06 2018 at 20:51)</a>:</h4>
<p>There's already an unreachable code lint</p>



<a name="146893471"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893471" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893471">(Nov 06 2018 at 20:52)</a>:</h4>
<p>oh good point</p>



<a name="146893489"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893489" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893489">(Nov 06 2018 at 20:52)</a>:</h4>
<p>I had misremembered and thought the unreachable code only complained about the assignment, but it does complain about the binding itself.</p>



<a name="146893533"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893533" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893533">(Nov 06 2018 at 20:53)</a>:</h4>
<p>so maybe a 'fix" here is easier than I thought:  make the unused_mut lint only fire if the declaration in question is also reachable (according to whatever logic the unreachable_code lint uses) ?</p>



<a name="146893561"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893561" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893561">(Nov 06 2018 at 20:54)</a>:</h4>
<p>(here's my demo of it complaining about the binding itself: <a href="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2018&amp;gist=71bc31136387eed6ced2b3462d8494b8" target="_blank" title="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2018&amp;gist=71bc31136387eed6ced2b3462d8494b8">play</a>)</p>



<a name="146893688"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893688" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893688">(Nov 06 2018 at 20:55)</a>:</h4>
<p>There's also the issue of something like</p>
<div class="codehilite"><pre><span></span><span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sum_nan</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">assert_eq</span><span class="o">!</span><span class="p">(</span><span class="n">v</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span><span class="w"></span>
<span class="w">    </span><span class="kd">let</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">assert_eq</span><span class="o">!</span><span class="p">(</span><span class="n">v</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>



<a name="146893705"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893705" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893705">(Nov 06 2018 at 20:55)</a>:</h4>
<p>This would still be a "regression" in cases where the unreachable code itself does not contain any mutations of the local (and thus one might argue that the <code>unused_mut</code> lint "should" fire) ; as demonstratred here <a href="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2015&amp;gist=0c80c87a3b0d9ac547528ee6dae4b872" target="_blank" title="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2015&amp;gist=0c80c87a3b0d9ac547528ee6dae4b872">play</a></p>



<a name="146893801"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893801" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893801">(Nov 06 2018 at 20:56)</a>:</h4>
<p><span class="user-mention" data-user-id="116118">@Matthew Jasper</span>  your example still fires warning: variable does not need to be mutable under the 2015 edition.</p>



<a name="146893808"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893808" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893808">(Nov 06 2018 at 20:57)</a>:</h4>
<p><a href="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2015&amp;gist=46928cd7c01b70fd64bda318016c0bd0" target="_blank" title="https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2015&amp;gist=46928cd7c01b70fd64bda318016c0bd0">https://play.rust-lang.org/?version=nightly&amp;mode=debug&amp;edition=2015&amp;gist=46928cd7c01b70fd64bda318016c0bd0</a></p>



<a name="146893856"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893856" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893856">(Nov 06 2018 at 20:57)</a>:</h4>
<p>Interesting</p>



<a name="146893923"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893923" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893923">(Nov 06 2018 at 20:58)</a>:</h4>
<p><span class="user-mention" data-user-id="116107">@davidtwco</span> maybe part of the task for <a href="https://github.com/rust-lang/rust/issues/55344" target="_blank" title="https://github.com/rust-lang/rust/issues/55344">#55344</a> would be to engage with any potential stakeholders who work on these lints and get their input on what they think the "right" (or "best", or "acceptable") behavior is</p>



<a name="146893945"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893945" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> davidtwco <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893945">(Nov 06 2018 at 20:58)</a>:</h4>
<p>Sure thing.</p>



<a name="146893947"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146893947" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146893947">(Nov 06 2018 at 20:58)</a>:</h4>
<p><span class="user-mention" data-user-id="116118">@Matthew Jasper</span> yeah at this point I'm not sure I grok what is going on here</p>



<a name="146894057"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146894057" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146894057">(Nov 06 2018 at 21:00)</a>:</h4>
<p>okay well anyway I've managed to fill up 29 minutes with relative nonsense. :)</p>



<a name="146894116"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146894116" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146894116">(Nov 06 2018 at 21:00)</a>:</h4>
<p>Are there any topics you all wanted to discuss?</p>



<a name="146894314"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146894314" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Matthew Jasper <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146894314">(Nov 06 2018 at 21:02)</a>:</h4>
<p>No, I'll happily have another week not working on NLL compiler issues.</p>



<a name="146894613"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/weekly%20meeting%20November%206/near/146894613" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/weekly.20meeting.20November.206.html#146894613">(Nov 06 2018 at 21:06)</a>:</h4>
<p>okay then I'm going to call this meeting over. THanks you both for attending!</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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